Many buildings, especially skyscrapers, use a significant amount of air conditioning to keep their interiors cool. Electronic window shades or tinting rely on an external power source, and thus, wiring many windows becomes problematic. These smart window applications depend on an applied bias to hold the transparent state; without power the windows default to opaque.
Some self-powered devices, for example, photoelectrochemical (PEC) devices, use incident light and photoconductors to generate electron-hole pairs and cause chemical reactions to generate energy; however, these devices rely on external circuits to move electrons. It would be desirable to develop a self-powered system that does not rely on an external circuit, and rather operates in an open circuit condition.
In other window applications, a self-powered sun shade has been shown to be problematic. The sun shade utilizes liquid crystals, but these crystals degrade over time and thus have a limited life span. Thus, it would be desirable to develop a self-powered open circuit sun shade with longer lasting components.